For elongated conduit or duct type apparatuses for passage of material therethrough, it is common for the material passing through such conduit to incompletely to fill certain internal portions thereof so as to cause formation of air pockets therein. For example, elevated portions of a curved conduit have been found to be particularly susceptible to formation of air pockets in internal sections thereof. This susceptibility of air pocket formation can occur in a variety of environments or areas and typically does not depend on the type of material passing through the conduit.
Post-tensioning apparatuses or systems for concrete or other suitable structures typically utilize elongated conduits or ducts for passage of a hardenable material such as grout through the conduit. Since it is also common for post-tensioning apparatuses to include curved conduits comprising portions of higher and lower elevations, such post-tensioning apparatuses have particular susceptibility to formation of air pockets in elevated portions thereof where grout will usually not completely fill. As can be appreciated by those of skill in the art of post-tensioning apparatuses and methods, it has therefore been common in the past to utilize vertical vent pipes which communicate with elevated, curved portions of an elongated conduit on one end and communicate on the opposite end with environment outside the material, such as concrete, that surrounds the post-tensioning system in order to pass grout through the vent pipe to completely fill the conduit, including the elevated portions thereof.
The use of such vent pipes suffers from many disadvantages, including forming a weak point in the post-tensioning system, acting as a natural pathway for contaminants to enter the internal portions of the post-tensioning system such as de-icing salts, and also providing much difficulty in the concrete pouring and finishing processes. Even in post-tensioning systems of the type disclosed in Parent patent application U.S. Ser. No. 08/797,690, commonly owned herewith and specifically incorporated by reference herein, there typically are body section portions adjacent to an intermediate anchor head which typically are prone to formation of air pockets in internal portions thereof despite the use of a transfer means for routing grout from a first body section, around and past the intermediate anchor head, and into an adjacent, second body section.
In light of the prior art as discussed hereinabove, it is apparent that there remains much room for improvement in the art of venting and preventing formation of air pockets in conduit or duct type apparatuses for passage of material therethrough, particularly for post-tensioning systems for concrete or other suitable structures.